Comparison of Catalytic Applications of CaO-Ag Bimetallic Nanoparticles and Its Composite: CaO-Ag/Na-alg/PANI

Silver (Ag) particles embedded on the surface of calcium oxide (CaO) bimetallic nanoparticles (BNPs) are synthesized using a chemical reduction method. Bio-waste eggshells were used as the source of CaO, while silver nitrate (AgNO₃) was used to provide Ag for the preparation of CaO-Ag BNPs. The nanocomposites CaO-Ag/Na-alg, CaO-Ag/PANI and CaO-Ag/Na-alg/PANI were fabricated via an in-situ polymerization method. The crystalline nature of the BNPs and nanocomposites was revealed by X-ray diffraction (XRD) analysis, showing the following order of crystalline nature: CaO > Ag > PANI > Na-alg. Scanning electron microscope (SEM) images showed that irregular shapes were exhibited by the CaO-Ag BNPs and that Ag particles, reduced from AgNO₃ in the presence of NaBH₄ were embedded on the surface of the CaO particles. Energy dispersive X-ray (EDX) spectroscopy confirmed that only Ca, O and Ag elements were contained in the synthesized of CaO-Ag BNPs. Essential functional groups were identified by Fourier transform infrared (FTIR) spectroscopy, with bands around 669, 868, 1077, and 1541 cm⁻¹ corresponding to CaO, Ag, Na-alg and PANI respectively. After characterization, the BNPs and nanocomposites were evaluated as catalysts for reducing different organic dyes. The catalytic performance was assessed by comparing different kinetic parameters, including the apparent rate constant (k_app), reduction time, % reduction and half-life. The best catalytic reduction of methyl blue (MB) was demonstrated by the CaO-Ag/Na-alg/PANI nanocomposite compared to other dyes. k_app of 0.181 min⁻¹, a % reduction of 86%, a reduction time of 18 min and a half-life of 4 min for MB dye was observed for the CaO-Ag/Na-alg/PANI nanocomposite.